Implantable medical devices may include a housing and a lead or catheter for delivering therapy to a treatment site within a patient's body. For example, a pacemaker may include a housing, or pulse generator, containing electronics and a battery; and an electrical lead extending from the pulse generator to a treatment site—the heart. In another example, a drug delivery system may include a housing, or drug delivery pump, containing the pump, a battery, and a supply of the drug; and a catheter extending from the drug delivery pump to the treatment site requiring the drug. In some cases, the housing may be installed in a subcutaneous pocket within a patient's body.
Implanting a medical device within a patient inherently exposes the patient to a risk of a nosocomial (e.g., hospital-acquired) infection associated with bacteria adhering to the exterior of the medical device. For example, the average nosocomial infection rate associated with the implantation of pacemakers and implantable cardioverter defibrillators is approximately 3%. In some cases of infection, the implantable medical device, including a device housing and any associated electrical leads or catheters, must be completely removed. Following removal, the infection must be cured and the patient must heal enough to tolerate implantation of a replacement medical device. The costs of such infections are significant, not only intrinsically, but also in terms of the physical and emotional stress suffered by the patient.
Once implanted, the external surface of the medical device may also serve as an attachment point for red blood cells and platelets to coagulate. Should the coagulated red blood cells and platelet break off of the medical device and lodge within a blood vessel forming a blood clot, or thrombus. This thrombosis may restrict the flow through the blood vessel and endanger the patient.
What is needed is a way to prevent infections and thrombosis which may result from implanting a medical device within a patient.